The benzimidazoles, including triclabendazole, are well known for their anthelmintic activity. Of all the benzimidazoles known, triclabendazole is particularly useful, as it is highly effective against liver flukes at all stages of their life cycle. Albendazole, in contrast, is only effective against adult flukes.
Triclabendazole, is also known as 5-Chloro-6-(2,3-dichlorophenoxy)-2-methylthio-1H-benzimidazole, and represented by Formula I.

Ruminants, such as sheep, cattle and goats, are susceptible to Fasciola, the disease caused by parasitic liver flukes, and it is important that formulations effective against the disease are available. In particular it is advantageous to have liquid formulations which contain the active anthelmintic in solution and which are easily administered by way of a pour-on.
It has been difficult to provide liquid formulations containing triclabendazole due to the highly insoluble nature of the compound. This has resulted in anthelmintic formulations containing triclabendazole being prepared as suspensions. Suspension formulations have a number of disadvantages. The most serious relates to stability. Veterinary formulations may be stored for extended periods in large, opaque containers and must be stable. Suspensions tend to be unstable in that the actives tend to settle out of the formulation. This causes problems as it results in differences in concentration of the active through the formulation. This is turn leads to difficulties in determining the effective and safe doses for treatment of livestock. Suspensions are also less able to be absorbed when applied by way of a pour-on. Pour-ons must be formulated to penetrate the skin which is the body's natural barrier. While a suspension may be absorbed from the digestive tract the same formulation applied to the skin would be less able to be absorbed. By developing suitable liquid formulations particularly with solvents which have a good affinity for penetrating skin the active is more likely to be absorbed. With most actives applied as pour-ons to the dermis the dose rate at which it is applied is increased when compared to an oral or injectable formulation. This is to make up for the less efficient absorption through skin tissues.